A veritable army is on hand to protect a shipment of $10,000,000. But the convoy unknowingly is guarding bundles of scrap paper. The money is concealed in a Rolls Royce seemingly carrying two diplomats. The elaborate decoy is a plan by Inspector Ginco (MICHEL PICCOLI) to thwart his arch enemy, the master criminal Diabolik (JOHN PHILLIP LAW). But as the limousine arrives at the port to discharge its precious cargo, it is enveloped by a multi-colored smoke screen. When the smoke clears, the car is seen suspended from a crane, and perched on its roof, is Diabolik.

Travelling first by speedboat and then in his black Jaguar, Diabolik speeds away with the money. Waiting in a white Jaguar is his sweetheart and accomplice, the beautiful Eva (MARISA MELL). Later, the Minister of the Interior (TERRY THOMAS) appears at a press conference to announce that the death penalty will be imposed on convicted criminals.

Inspector Ginco is given emergency power and he clamps down on the underworld

with such fury that, in order to escape his wrath, syndicate boss Ralph Valmont (ADOLFO CELI) agrees to cooperate with the police in apprehending Diabolik. For Eva's birthday, Diabolik promises he will make her a present of a priceless emerald necklace now in the possession of the wife of the British Finance Minister.

Diabolik, playing human fly, scales the walls to the room of the British Minister and his wife, foils the television cameras and makes off with the necklace. But Eva is injured slightly during the getaway and when she visits a doctor, Valmont's mobsters seize her. Diabolik is informed by telephone that he can ransom her by turning over the $10,000,000 and the emerald necklace. He agrees.

Diabolik meets Valmont aboard his private plane. After taking off, he hands over the ransom and then is ordered to parachute from the plane to a spot where Eva supposedly is waiting. Suspecting a trick, Diabolik takes Valmont with him, through the bomb bays. As they fall the plane explodes; Diabolik had planted a bomb. He now refuses to pull the ripcord until Valmont divulges the details of the trap. He knocks out his adversary and then rescues Eva from a cabin, just as Inspector Ginco and an army of police and soldiers move in. lie orders Eva to escape and he holds off Ginco's men with a submachine gun. After tampering with the ammunition clip in the seclusion of a cave, he guns down Valmont and then swallows a gold capsule.

The inspector, somewhat saddened by the death of his long time foe, holds a press conference to announce Diabolik's demise, while a doctor prepares for an autopsy. His assistant actually Eva-injects a fluid into Diabolik's arm, and suddenly the "corpse" is resurrected. Diabolik explains he has utilized an old Indian drug which suspends life for 12 hours.

The government must sell some of its gold reserve. But Ginco is determined, Diabolik will not get the gold. He has it melted into a 20-ten ingot and encased in steel, and under elaborate precautions, begins shipment by railroad car.

Diabolik, by blowing up a tunnel, reroutes the train onto a mined bridge, which he then detonates. The train plunges into the waters, but Ginco escapes. Using an undersea plane and balloons to float the ingot, Diabolik and Eva recover it and move it to their hideout. But Ginco has placed radioactive materials in the steel case and he is able to trace Diabolik to his headquarters. The police and military move in. By superior firepower, he is driven back toward the melting gold. The steel cast bursts . . . .